The invention generally relates to broadband telephony networks. In particular, the invention relates to routing telephony connections in a broadband network.
FIG. 1 illustrates a telephony network 10. Telephone users of the broadband network use telephones 121 to 12n connected to communication gateways (CGs), 141 to 14m, to make telephone calls. The CGs 141 to 14m are used as an interface between the telephones 121 to 12n and the rest of the network 10.
The CGs 141 to 14m are connected to an Internet protocol (IP) network 18 through a cable modem termination system 16 interfacing between the CGs 141 to 14m and the IP network 18. The IP network 18 transfers packets of data. Each packet is sent in an assigned mini-slot of a frame in the network 18. Each packet carries communication data, such as encoded voice data, and overhead and routing data, such as a destination address.
The IP network is connected to the public switched telephone network (PSTN) 28 via a PSTN/IP network gateway 26. Telephone users 301 to 30j using telephones outside the broadband network can communicate with broadband network telephone users 121 to 12n through the PSTN 28.
The simplified hardware of a CG 141 to 14m is shown in FIG. 2. The CG 141 to 14m has an RF connector 32 to receive RF signals from and transmit RF signals over the broadband network 10. A tuner/amplifier 34 and a cable modem 36 are used to convert the received RF signals into digital baseband signals and digital baseband signals into RF signals for transmission. The CG 141 to 14m also has a digital signal processor (DSP) 38 and codec 40 for processing voice signals. A processor 42 along with a random access memory (RAM) 44 and non-volatile memory (NVMem) 46 are used to perform many functions, such as performing commands as directed by the call management system 20.
To handle the overhead functions of the IP network 18, a network management system 22, an operating support system 24 and a call management system 20 are used. The call management system 20, “call agent”, controls telephony calls sent through the network 18. If a call or a multiparty call extends over multiple networks call managers 20 in the different networks are used to facilitate communications between the networks. Typically, the party placing the call is the “control party” and its call manager 20 controls the call connections. Additionally, depending on the size and design of a network a single network may have one or multiple call managers 20.
The simplified hardware of a call management system 20 is shown in FIG. 3. The call management system 20 comprises a call agent and a RF connector 48. The call agent 48 controls various functions of call management system 20 and interacts with other modules 22,24. Call signaling 50 sends commands to control components of the network, such as the CGs 141 to 14m. Other components of the call management system 20 for use in performing its functions are the communications stacks 52, network interface module (NIM) 54, processor 58, RAM 60, non-volatile memory 62 and permanent storage 56.
One call agent function is to establish telephone connections between the telephone users 121 to 12n. FIGS. 4a to 4d are a flow chart and illustrations of establishing a three-way telephone call. As shown in FIG. 4b, a bi-directional connection is established between telephone user 1, T1 121 and telephone user 2, T2 122. Each bi-directional connection has two opposing one-way connections. Each one-way connection in the network has an origin, a destination and at least one assigned mini-slot. Based on the bandwidth required for a connection and a network's allocation rules, multiple mini-slots may be assigned to a connection.
T1 121 initiates a three-way call by placing T2 122 “on hold” and placing a call to telephone user 3, T3 123. As shown in FIG. 4c, the “on hold” connection between T1 121 and T2 122 is maintained but inactive (as shown by dashed line). A bi-directional connection is established between T1 121 and T3 123, 68. When T1 121 initiates a three-way call, both bi-directional connections (T1/T2 and T1/T3) are broken, deleted. Simultaneously, three new bi-directional connections are established to a network bridge 64 (T1/bridge, T2/bridge and T3/bridge), 70. The network bridge 64 can be located anywhere within the telephony network 10, which includes the broadband network, the IP network 18 and the PSTN 28. One function of the network bridge 64 is to mix the messages from multiple users to be sent to one of the users. To illustrate for user T2 122, all three users T1 121, T2 122 and T3 123 send messages to the bridge 64. The bridge 64 sends the combined messages of T1 121 and T3 123 without T2's message to T2 122. Using the network bridge 64 eliminates the need for the telephone users 121 to 12n to mix voice signals. For instance, T1 121 does not need to send T3 123 both T1's and T2's mixed voice signals.
Using the network bridge 64 also has drawbacks. When the T1/T2 and T1/T3 connections are broken, the network 10 may not have adequate bandwidth to establish the three new bi-directional connections. Initially, there are four one-way connections (two bi-directional connections) between T1 121, T2 122 and T3 123. After establishing connections to the bridge 64, six (6) one-way connections (three bi-directional connections) are established requiring additional bandwidth for the two extra one-way connections. Furthermore, due to the mixing at the bridge 64, the connections originating from the bridge 64 may use higher rate voice coders requiring additional bandwidth. As a result, all of the connections may be lost. Accordingly, it is desirable to have alternate approaches to multi-user connection.